Chapter 1 provides a general introduction to addition radical polymerizations and controlled/living radical polymerizations with an emphasis on nitroxide-mediated polymerization (NMP). The merits of supercritical carbon dioxide (scCO2) as a polymerization medium are described, focusing on heterogeneous NMP systems.
Chapter 2 describes the work published in, Macromolecules 2009, 43, 914-919. The point of particle nucleation or the critical degree of polymerization (Jcrit) at which polymer chains become insoluble in the continuous medium (scCO2) has been ascertained under a variety of experimental conditions for the precipitation NMP of styrene (St) and tert-butyl acrylate (t-BA), mediated by SG1. A simple graphical model has been developed and successfully employed, whereby Jcrit can be predicted as a function of both target molecular weight and initial monomer loading. Jcrit is shown to increase linearly with increasing pressure.
Chapter 3 details the work published in, J. Polym. Sci. Part A: Polym. Chem. 2011, 49, 1856-1864. Chain transfer to solvent has been investigated in the conventional radical polymerization (RP) and NMP of N-isopropylacrylamide (NIPAM) in N,N-dimethylformamide (DMF) at 120 °C. The same chain transfer to solvent constant (Ctr,S) can account for the deviation of experimental molecular weight data from theoretical, in both conventional RP and NMP.
Chapter 4 gives an account of the work published in, J. Polym. Sci. Part A Polym. Chem. 2011, 49, 1719-1723. The first controlled/living inverse suspension polymerization in scCO2 is described. The NMP of NIPAM proceeded in the absence of stabilizer to high conversion with low polydispersity, affording a dry powder. The purification step entails washing with fresh scCO2, and the technique thus completely avoids of the use of environmentally damaging volatile organic compounds.
Chapter 5 presents the work published in, Eur. Poly. J. 2012, doi.org/10.1016/j.eurpolymj.2012.04.011. A new preparation of thermoresponsive poly(NIPAM) containing block copolymers, involving two successive heterogeneous controlled/living NMPs in scCO2 is described. Precipitation NMPs in scCO2 give functionalised macroinitiators (MIs), and a first report of the controlled/living NMP of N,N-dimethylacrylamide in scCO2 is described. The MI initiates an inverse suspension NMP of NIPAM in scCO2. Aqueous cloud point temperature analysis for AB block copolymers show a significant dependence on poly(NIPAM) chain length.

Well defined polymer chains of specific, targeted chain length were polymerized for several monomers in the solvent, supercritical carbon dioxide. Supercritical carbon dioxide solvent was shown to be a superior medium for specific polymerizations due to physical and chemical advantages such as the absence of chain transfer to solvent. A predictive model for determining the point of particle formation in these systems was devised.